The present invention relates to a piercing needle, and more specifically, to a piercing needle having an improved piercing resistance by means of a surface treatment using silicone compounds.
Conventionally, there have been carried out techniques of treating a metal surface with a silicone compound to reduce frictional resistance thereof in various applications. For instance, it is known that a metal cutting blade can be coated with an adhesive coating containing as a main component a copolymer of an aminoalkylsiloxane and a methylsiloxane and maintained under heating or at normal temperature to cure the coating by cross-linkage (Japanese Examined Patent Publication No. Sho46-3627). The piercing resistance of a metal medical needle into a rubber plug or skin is reduced when the needle is coated with the coating substance. However, there arises a problem in that if the needle is repeatedly caused to pierce rubber plugs or skin, the coating substance is peeled off from the needle, thereby increasing the piercing resistance. The reason relates to the fact the coating substance is insufficiently cured. Further, the medical needle must be sterilized, but the piercing resistance of the needle coated with the coating substance may be increased even if it is sterilized by gamma ray irradiation.
The medical needle referred to herein means an injection needle or the like, which is repeatedly used to introduce liquid medicines contained in vials having rubber plugs into injection cylinders and to administer the liquid medicines in the injection cylinders into human bodies. The piercing resistance means the resistance at the time when the needle pierces the rubber plug or the skin. When the resistance is lower, the pain received by a human is less when the needle pierces human skin.
On the other hand, there is known an injection needle, which is obtained by coating a needle with a composition comprising as a main component a reaction product of a polydiorganosiloxane having a silanol group and a reaction product of an amino group-containing silane and an epoxy group-containing silane, and by maintaining the coating under heating or at normal temperature to thereby cure the composition (Japanese Examined Patent Publication No. Sho 61-35780). The composition provides excellent curing properties. However, there arise cases where the piercing resistance is not sufficiently reduced.
Also, there is known an injection needle, which is coated with a coating of a silicone mixture consisting of a silicone containing an amino group in a side chain and/or a terminal end thereof and a polydiorganosiloxane, and is treated on its surface by a curing process including gamma ray irradiation (Japanese Patent Application Laid-open No. Hei 7-178159). The gamma ray irradiation can accelerate the curing of the coating as well as sterilize the injection needle. However, if a sterilization process other than gamma ray irradiation is employed, the coating is not sufficiently cured, and the piercing resistance increases when the needle repeatedly pierces into rubber plugs or the skin.
In view of the above-mentioned problems, the inventors of the present invention discovered a piercing needle, which is coated with a mixture of a silicone obtained by reaction of an amino group-containing alkoxysilane, an epoxy group-containing alkoxysilane and a silicone having silanol groups at both terminal ends thereof, and a non-reactive silicone (U.S. Pat. No. 6,015,398). The piercing needle has a low piercing resistance into rubber plugs or skin, and further has no limitation on its method of sterilization, which is a superior point. However, there has been desired a further improvement so that the piercing resistance becomes better when the piercing needle repeatedly pierces into rubber plugs or the skin.
In consideration of the above-mentioned circumstances, an object of the present invention is to provide a piercing needle having a low piercing resistance even if the needle repeatedly pierces into rubber plug or the skin.
The inventors of the present invention have made an intensive investigation to solve the above-mentioned problems. As a result, they found that an intended purpose of the present invention can be accomplished by a technique in which a piercing needle is coated with a silane coupling agent, and then coated with a specific silicone mixture. The present invention has been completed based on this finding.
That is, the present invention relates to a piercing needle having an outer surface coated with a compound containing a silane coupling agent, characterized in that the outer surface is further treated with a mixture of a reactive silicone and a non-reactive silicone.